In recent years, X-ray Computed Tomography (CT) apparatuses that employ a photon-counting-method detector have been developed. Unlike integral-type detectors employed in conventional X-ray CT apparatuses, photon-counting-method detectors are configured to count photons derived from X-rays that have passed through an examined subject (e.g., “patient”) for each of predetermined energy bands. Such X-ray CT apparatuses are configured to reconstruct an X-ray CT image based on a photon counting result.